深圳福田红树林鸟类自然保护区水禽生态环境的建设

论述了深圳福田红树林鸟类自然保护区水禽的种类、组成及其数量;水禽在保护区各地段的分布、繁殖规律、种类数量的变化及其变化原因;并阐明水禽生态环境建设的重要性及其建设措施。     

Physiology of cold hardiness in cocoons of five earthworm taxa (Lumbricidae: Oligochaeta)

Earthworm cocoons are mostly found in the uppermost soil layers and are therefore often exposed to low temperatures during winter. In the present study, cocoons of five taxa of earthworms were investigated for their tolerance to freezing, melting points of cocoon fluids and dehydration of cocoons when exposed to a frozen environment. Embryos of the taxa investigated were freeze intolerant. The melting points of fully hydrated cocoon fluids were high (above –0.3°C) and thermal hysteresis factors were absent. Exposure to a frozen environment caused the cocoons to dehydrate drastically and dehydrated cocoons showed significantly lower super-cooling points than fully hydrated cocoons, reducing the risk of freezing for dehydrated cocoons. It is proposed therefore that the cold-hardiness strategy of the earthworm cocoons is based on dehydration upon exposure to subzero temperatures in the frozen environment. Cocoons of three surface-dwelling taxa, Dendrobaena octaedra, Dendrodrilus rubidus tenuis and Dendrodrilus rubidus norvegicus had lower supercooling points and survived frost exposure better than cocoons of two deeper-dwelling taxa, Aporrectodea caliginosa and Allolobophora chlorotica. One of the investigated taxa, D. r. norvegicus, was collected from a cold alpine habitat. However, it was not more cold hardy than the closely related D. r. tenuis collected from a lowland temperate habitat. D. octaedra was the most cold hardy taxon, its cocoons being able to withstand –8°C for 3 months and –13.5°C for 2 weeks in frozen soil.Abbreviations dw dry weight - fw fresh weight - SCP supercooling point     

The effects of warming by active and passive means on the subsequent responses to cold water immersion

Two experiments were undertaken to investigate the effects of warming the body upon the responses during a subsequent cold water immersion (CWI). In both experiments the subjects, wearing swimming costumes, undertook two 45-min CWIs in water at 15° C. In experiment 1, 12 subjects exercised on a cycle ergometer until their rectal temperatures (T _re) rose by an average of 0.73°C. They were then immediately immersed in the cold water. Before their other CWI they rested seated on a cycle ergometer (control condition). In experiment 2, 16 different subjects were immersed in a hot bath (40° C) until their T _re rose by an average of 0.9° C; they were then immediately immersed in the cold water. Before their other CWI they were immersed in thermoneutral water (35° C; control condition). Heart rate in both experiments and respiratory frequency in experiment 1 were significantly (P < 0.05) higher during the first 30 s of CWI following active warming. In experiment 1, the rate of fall of T _re during the final 15 min of CWI was significantly (P < 0.01) faster when CWI followed active warming (2.46° C · h^–1) compared with the control condition (1.68°C · h^–1). However, this rate was observed when absolute T _re was still above that seen in the control CWIs. It is possible, therefore, that if longer CWIs had been undertaken, the two temperature curves may have converged and thereafter fallen at similar rates; this was the case with the aural temperature (T _au) seen in experiment 1 and the T _au and T _re in experiment 2. It is concluded that pre-warming is neither beneficial nor detrimental to survival prospects during a subsequent CWI.     

Best Linear Unbiased Prediction (BLUP) for regional yield trials: a comparison to additive main effects and multiplicative interaction (AMMI) analysis

Multilocation trials are often used to analyse the adaptability of genotypes in different environments and to find for each environment the genotype that is best adapted; i.e. that is highest yielding in that environment. For this purpose, it is of interest to obtain a reliable estimate of the mean yield of a cultivar in a given environment. This article compares two different statistical estimation procedures for this task: the Additive Main Effects and Multiplicative Interaction (AMMI) analysis and Best Linear Unbiased Prediction (BLUP). A modification of a cross validation procedure commonly used with AMMI is suggested for trials that are laid out as a randomized complete block design. The use of these procedure is exemplified using five faba bean datasets from German registration trails. BLUP was found to outperform AMMI in four of five faba bean datasets.     

Stress-Induced Sensitization of Dopamine and Norepinephrine Efflux in Medial Prefrontal Cortex of the Rat

Abstract: We examined whether prior exposure to chronic cold (17–28 days, 5°C) alters basal or stress-evoked (30-min tail shock) catecholamine release in medial prefrontal cortex, nucleus accumbens, and striatum, using in vivo microdialysis. Basal norepinephrine (NE) concentrations in medial prefrontal cortex did not differ between chronically cold-exposed rats and naive control rats (2.7 ± 0.3 vs. 2.5 ± 0.2 pg/20 µl, respectively). Basal dopamine (DA) efflux in any of the brain regions was not significantly different between chronically cold-exposed rats and naive rats. However, a trend for lower basal DA efflux in the cold-exposed relative to naive rats was observed in medial prefrontal cortex (1.5 ± 0.2 vs. 2.2 ± 0.3 pg/20 µl, respectively), nucleus accumbens (3.7 ± 0.8 vs. 5.4 ± 0.9 pg/20 µl, respectively), and striatum (4.4 ± 0.5 vs. 7.2 ± 1.5 pg/20 µl, respectively). In medial prefrontal cortex of rats previously exposed to cold, tail shock elicited a greater increase from baseline in both DA and NE efflux relative to that measured in naive rats (DA, 2.3 ± 0.3 vs. 1.2 ± 0.1 pg, respectively; NE, 3.8 ± 0.4 vs. 1.4 ± 0.2 pg, respectively). However, in nucleus accumbens or striatum of rats previously exposed to cold, the stress-induced increase in DA efflux was not significantly different from that of naive rats (nucleus accumbens, 1.8 ± 0.7 vs. 1.5 ± 0.3 pg, respectively; striatum, 1.9 ± 0.4 vs. 2.6 ± 0.7 pg, respectively). Thus, both cortical NE projections and cortically projecting DA neurons sensitize after chronic exposure to cold. In contrast, subcortical DA projections do not sensitize under these conditions.     

15N2 measurement of nitrogen fixation by legumes and actinorhizals: theory and practice

A gas-tight chamber has been constructed to calibrate the ¹⁵N isotope dilution method against direct ¹⁵N₂ measurements. The theoretical basis for such estimates is given, and the practical problems associated with the experiments are discussed.     

Perspectives on environmental risk assessment

Risk is by no means a simple concept. Natural variability and definitional problems with the concept of probability complicate the measurement and use of risk as an analytical tool. Variability requires that risk assessment methods separate natural from total risk when attempting to estimate anthropogenic risk. Failure to do so results in the over estimation of anthropogenic risk and the eventual loss of credibility for risk assessment methodologies. The common frequentist approach to probability is not consistent with anything but a modelling approach to risk assessment. When combined with its ability to account for natural variability, incorporate laboratory-assay data and offer complete statistical and experimental control, modelling is a promising approach to risk assessment. Modelling, however, is not without its drawbacks. Initialization bias can result in the over, or under, estimation of both natural and anthropogenic risk. Furthermore, model estimates are time dependent. The convergence of natural and anthropogenic risk poses problems for modelling-based risk assessment and requires clear statements as to the importance of the time dimension in risk assessment. When combined, the drawbacks to modelling-based risk assessment argue that risk should never be stated as a scalar quantity. Instead, modelling-based risk assessment should provide estimates of the complete range of risk measures (total, natural, and anthropogenic) as well as indications of convergence time. Only then can the modelling-based approach be viewed as the most appropriate means of carrying out scientifically credible risk assessment.     

冷锻炼和ABA诱导水稻幼苗提高抗冷性期间膜保护系统的变化

冷锻炼和ＡＢＡ处理提高了水稻幼苗叶绿体ＳＯＤ和ＧＲ活性及叶片抗氧化剂ＡｓＡ和ＧＳＨ的含量,降低了膜电解质泄漏,增强了幼苗的抗冷性．等电聚焦电泳分析表明,冷锻炼和ＡＢＡ处理苗叶绿体ＳＯＤ三条同工酶带和ＧＲ１、２、３和６同工酶带都有不同程度的增强．低温胁迫后,处理和未处理首的ＳＯＤ、ＧＲ活性和ＡＳＡ、ＧＳＨ含量均有所下降．但处理苗的水平仍维持在未处理苗之上．亚胺环已酮可抑制因冷锻炼和ＡＢＡ诱导增加的ＳＯＤ和ＧＲ活性,并使叶片电解质泄漏增大．本试验结果表明冷锻炼或ＡＢＡ诱导水稻幼苗抗冷性提高时,对防御活性氧的保护系统有类似的影响。